Method for the automatical recognition of characters



April 30, 1963 K. w. STEINBUCH 3,083,096

' METHOD FOR THE AUTOMATICAL RECOGNITION OF CHARACTERS Filed April 15,1958 11 Sheets-Sheet 1 FIGI RESISTANCE NETWORK CHECKING TRACK U SELECTORTRACK U 1 I l was 1 DIODES- 1: a; k EUT TRANS/LIATOR I F o| SELECTORTRACK M DET PRE R :gi LIMITERS I 1 L1 L1 \f I L 0% TRACK 3L) AMPLIFIERSA A A M 8 O9 PHOTOCELLS SELECTOR TRACK o 11 SHAPE A DETERMINER i To I:2% K TRACK l A O g GATES AREA 1 NUMERAL 2 INVENTOR K W. STEINBUCHATTORNEY April 30, 1963 METHOD FOR THE Filed April 15, 1958 K. w.STEINBUCH 3,088,096

AUTOMATICAL RECOGNITION OF CHARACTERS ll Sheets-Sheet 2 RESISTOR Fig. 7a

LIMITfR H RES/57M Fig. 74

RES\STOR t logic CI rcu/is NETWORK IMVENTOR. KQW. Stdnbuch April 30,1963 K. w. STEINBUCH 3,088,096

METHOD FOR THE AUTOMATICAL RECOGNITION OF CHARACTERS Filed April 15,1958 11 Sheets-Sheet 3 1* Km 2; "N @930 ttovo INVENTOR. KM. SteinbochApril 1963 K. w. STEINBUCH 3,088,096

METHOD FOR THE AUTOMATICAL RECOGNITION OF CHARACTERS 11 Sheets-Sheet 4Filed April 15, 1958 WZVW April 30, 1963 K. w. STEINBUCH 3,088,096

METHOD FOR THE AUTOMATICAL RECOGNITION OF CHARACTERS Filed April 15,1958 11 Sheets-Sheet 5 DIODE U W ROTARY SWITCHES RESISTOR NETWORKLIMlTERS 8 5M0 eIemenTL p p2 X+1 px 1 PK X-1 Ev \Shape element April1963 K. w. STEINBUCH 3,088,096

METHOD FOR THE AUTOMATICAL RECOGNITION OF CHARACTERS Filed April 15,1958 11 Sheets-Sheet 6 14 b 13 x 12 11 a 1o 9 Fig.5 8 m Fig.6

V B I: I I r Pumas \AMPLIFIER \LIMH'ER JNVENTOR. 1w. Stdnbuqh April 30,1963 K. w. STEINBUCH 8 METHOD FOR THE AUTOMATICAL RECOGNITION OFCHARACTERS Filed April 15, 1958 11 Sheets-Sheet 7 0 Fig.8

RESISTOR INVENTQR. KM. Stembuch April 30, 1963 K. W. STEINBUCH METHODFOR THE AUTOMATICAL RECOGNITION OF CHARACTERS 11 Sheets-Sheet 8 FiledApril 15, 1958 BB BATTERY RESISTOR Mr E +O T\-CAPAC\TOR RESISTOR ME ME.!-0 MA INVENTOR Kktsteinbvdl ATTORNEY April 30, 1963 K. w. STEINBUCH3,088,096

METHOD FOR THE AUTOMATICAL RECOGNITION OF CHARACTERS Filed April 15,1958 11 Sheets-Sheet 9 STORAGE RE$\$TOR UXFI Q R a I 1 O- U TRANSISTORmp PHOTOcELL F AMPLIFIER v LIMITER B Di STQZE 3 s Q STORAGE 5% (U0 0DEV/CE IBATTEAY P F i g- 77 KEY ifih v 7%JW BY ATTORNEY April 30, 1963K. w. STEINBUCH METHOD FOR THE AUTOMATICAL RECOGNITION OF CHARACTERSFiled April 15, 1958 11 Sheets-Sheet 10 mobjwzqmh 3 uuc @5 5 E mus uu uIN V EN TOR. KM!- stzinbvch April 30, 1963 K. w. STEINBUCH 3,088,096

METHOD FOR THE AUTOMATICAL RECOGNITION OF CHARACTERS Filed April 15,1958 11 Sheets-Sheet 11 IN V EN TOR. KMLSiZinbuCh United States Patent3,t)$8,t 96 METHOD FQR THE AUTOMATICAL RECGGNE- TION 0F CHARACTERS KarlWilhelm Steinbuch, Fellbach, Germany, assignor to International StandardElectric Corporation, New York, N.Y., a corporation of Delaware FiledApr. 15, 1958, Ser. No. 728,732 Claims priority, application GermanyApr. 17, 1957 21 Claims. (Cl. 340-1463) This invention relates to anautomatic character recognition method.

In the course of applying automation to calculating and similarprocesses it is in many cases desirable that visually readablecharacters are also directly mechanically readable in order to controlthe corresponding equipments in the data-processing systems. This desirehas led to many proposals concerning the mechanical reading of lettersand figures.

In some of the conventional methods the characters are scannedphoto-electrically along certain horizontal and/or vertical lines, thusdetermining the black-white transitions. By suit-ably selecting thescanning lines electrical characteristics for the individual characterswill result, representing a definite code of the respective character.Of course, this encoding is entirely arbitrary and therefore, as a rule,also ditficult to survey. Instead of the optical scanning it has alsobeen proposed to print the characters with an electrically conductive ormagnetic ink, or the like, and to carry out the scanning alongpredetermined lines with the aid of corresponding sensing elements.

Another conventional scanning method consists in determining the blackcontents within the type field. This, however, may result under certaincircumstances, in characteristics or criterions for the individualcharacters, which are very difiicult to distinguish. A third method forrecognizing characters operates on the basis of the comparison ofcharacters with standard, stored characters. Generally, however, thismethod requires a large amount of equipment.

Finally, there is another method, according to which the line traces ofthe characters are utilized as distinguishing characteristics. In thismethod, however, one faulty interruption in the trace of the line of thecharacters will have a very disturbing effect. To avoid faultyevaluations very complicated processes are usually required fordetermining that the line interruption is actually not due to thecharacter itself.

Furthermore the conventional methods generally bear the disadvantage ofbeing sensitive to changes in size, displacements or twistings(distortions) of the characters. The aforementioned disadvantages arelargely eliminated by the novel method, in that this method, within widelimits, is invariable or unaffected by the aforementioned alterations orvariations.

An object of the invention is a method for the automatic recognition ofcharacters in particular of letters and figures. According to theinvention the characters to be recognized are electrically simulated ina field of potential and the then resulting field of potential isevaluated.

The field of potential may be suitably approximated in an electricalnetwork, which for example, consists of a network of concentratedimpedances disposed in coordinate rows and columns. The crossing pointsof the impedances, which may either be simple or complex, will then beacted upon by a fixed potential in accordance with the shape of thecharacters. When the periphery of the network is held at another fixedpotential, a potential field and current flow depending upon the shapeof the scanned character will appear. Therefore, the measurement of thepotential difference at definite points of the network, may be utilizedas a characteristic for the recognition of the characters.

By way of example, the simulation of the characters in the resistornetwork may be effected in that the characters are scanned in araster-shaped manner by one or more photocells, and that to each partialsurface of the raster (b one point (P of the network is assigned, andthat to those points (P whose associating partial area or surface (beither exceeds or undercuts a predetermined blackening, a voltage U isimpressed.

A further embodiment of the invention consists in that the charactersare divided in such shape elements that the potential conditions, whichare caused by these elements, can easily be evaluated for recognizingthe characters; it may then be possible to restrict the evaluation tosome very distinct horizontal or vertical lines. This, in turn, bringsabout a simplification of the evaluating methods and evaluating circuitarrangements. The characters may be divided in such a way that the shapeelements are unambiguously determined by the formation of the spatialderivatives of the first and second and probably even higher order ofthe potential values measured along the scanning lines, so that thesemay be assigned to the characters in a corresponding arrangement.

In elaborating upon this idea it is possible to recognize the numerals 09 by dividing them in three different shape elements, namely in a shapeelement that is open toward the left, hereinafter symbolically indicated(by L, in one that is open toward the right, indicated by R, and in onethat is closed, indicated by G, and in that the measuring of the fieldof potential is accomplished along three horizontal lines of reference,which are common to all figures. In the course of this it is suflicientto set up the first and the second derivative, which may be approximatedin that the potentials are determined at threepointsin the direction ofscanning on each of the three scanning lines, and are brought into acorresponding relation with respect to one another. The shape elementsand, consequently, the numerals, may then be unambiguously recognized bybringing the scanning results separately for each scanning trace for theshape element L into the relations x m-1+ x1) for the shape element Rinto the relations x1 x x+1 x (UM-1+ x-l.) and finally for the shapeelement G into the relations wherein U indicates the photocell outputpotential of the respective partial area of surface b U the potentialappearing at point P y of the potential field, and U the potentialimprinted upon the point P The invention as well as further advantagesand features thereof will be described in the following by way ofexample and with reference being bad to FIGS. 1 through 14 of thecopending drawings, in which:

and

and

FIG. 1 is a general layout of one embodiment of the V FIG. 4 shows thepotentials at three points of the resistor arrangement immediatelysuccessive in the x-direction with the potentials for the shape elementsL and R,

FIG. 5 shows the FIGURE 2 within a raster pattern for the areaquantizing of the scanning,

FIG. 6 shows a photocell amplifier/limiter arrangement serving both thescanning of the raster pattern and the digitizing of the scanning,

FIG. 7 shows a resistor arrangement with a diode input of theoutput-signals of the photocell arrangement according to FIG. 6,

FIG. 8 shows a selector arrangement for checking the potential field atthree points of the resistor arrangement immediately successive in thex-direction,

FIG. 9 shows five varieties of electronic gates which may be used forthe selectors Dr Dr according to FIG. 8,

FIG. 10 shows a circuit arrangement for determining the shape elements Land R according to the output-signals of selectors Dr Dr in FIG. 8;

FIG. 11 shows a circuit arrangement for determining the shape element Gaccording to the output-signals of the selectors Dr and D11 in FIG. 8;

FIG. 12 shows a translator for evaluating and trans lating theoutput-signals S R and S from FIGS. 10 and 11 to the numerals 0 9,

FIG. 13 shows the numerals 1 9, 0 with the current stages; and

FIG. 14 shows a circuit arrangement for measuring the current flowinginto a point P Prior to explaining the invention it is appropriate toconsider some facts regarding the potential theory as well as therecognitions on which the invention is based (cf. e.g. Kiipfrniiller,Einfiihrung in die theoretische Elektrotechnik, chapter III/6; Proc.IEE, vol. 96, page 163, vol. 98, page 486; Proc. IRE, August 1952, page970; Free. IEE, vol. 101, part II, page 349 et seq.).

The potential field of a plane plate (or matrix: a matrix being, insofaras we are interested here, a two or three dimensional body in which afield is capable of being developed) of uniform electric conductivitydepends upon the field margins existing therein, when assuming that atinfinity the potential zero exists, and at the field margins apredetermined constant potential U In this way the potential isdetermined at each point by the geometrical shape of the field margins.On the other hand, the measuring of the potential and of its spatialdifferential quotient at any point permits one to arrive at unambiguousconclusions as to the geometrical shape of the margins. It is to benoted that precise derivatives are not necessarily requisite; potentialchanges are also indicative of the field slope and what is sought is afield gradient (which, broadly speaking, includes either of the above)that may be utilized to determine the shape of the field margins.

With the aid of conventional circuit elements a plane field of flow asis the case with the electrolytic tank cannot be realized but a usefulapproximation thereof may be obtained.

FIGURE 1 is a general layout of one embodiment of the invention, asshown in FIGS. 1a through 12.

The character to be scanned is the numeral 2, shown in the lowerleft-hand side of the figure. The photocells convert discreteblack-white areas of the figure into electric energy which is amplified,limited and then passed on to coordinate points of a resistor matrixthrough the diodes, as shown. Since the resistor network has itsperiphery grounded, the potentials impressed upon the coordinate pointswill create a field of potentials throughout the network.

The network is now scanned along three tracks a, m and 0. In track It,for example, successive coordinate points in the matrix in the Xdirection are sampled to determine the potential gradient of the field.Since this gradient is quite dependent upon the concentration ofpotentials it may be analyzed in the shape determiner, shown in thefigure, which then stores 1 of 3 possible conditions; shape opened tothe left, shape opened to the right, and shape closed. The resultsstored in each of the three shape determiners corresponding to the threetracks are then led to a translator which, through a series of gatecircuits, sets a potential on one of the ten wires, 1 through 0.

Referring now to FIG. la there is shown a simple approximationobtainable by means of a coordinated arrangement of resistors. In thiscase the resistors do not necessarily need to be real, in some casescomplex resistors are likely to be of advantage. The potential U of thefield margins is in this case fed to the intersecting points P FIG. 2shows some field margins which may be part of the numerals 0 9 to berecognized. In the first line beneath the illustrations of the fieldmargins there are shown the potentials which are capable of beingadjusted and, consequently, measured e.g. along the checking track m,corresponding to a number of resistors of FIG. la. 'In the second andthird line there are respectively given the first and the secondditierential quotient. According to these differential quotients themargins are divided into the four shape elements W, L, R and G. Theseletters are assigned to the following geometrical shapes:

W :straight margin,

L=margin opened towards the left, R=margin opened towards the right, andG=closed margin.

The invention is now based on the further recognition that these shapeelements may be assigned to the ten numerals 0 9 in such a way that anunambiguous recognition of the numerals will be rendered possible. Tothis end, however, one checking track is not sufficient, but at leastthree of them are required.

FIG. 3 shows the numerals 0 9 with the three checking tracks 0, m, andu. Each checking track is assigned to one line of resistors of FIG. 1a.

TABLE I Checking Tracks Numeral upper middle lower L, R, G R. L. G. L.G.

G. L. G.

Table I shows the shape elements respectively resulting on the threechecking tracks with respect to the numerals l 9 and O. From this it maybe seen that the numerals can be unambiguously recognized from the shapeelements. Further it will be seen that the numeral 1 can be determinedby the absence of the shape elements L, R, and G (indicated in the TableI by i, R G) on all of the three checking tracks, so that the shapeelement W is not required for the numeral recognition, because it is notpresent in the other numerals. Finally it will be seen from Table I thatthe middle checking track 111 is only necessary for the distinguishingthe two numerals O and 8.

As a result of these theoretical considerations it is concluded: thecharacters to be recognized, and which are simulated in the potentialfield, can be imagined to be composed of shape elements by whichcharacteristic potential conditions are produced in the potential field;

accordingly, the shape elements may be determined from the potentialfield and assigned to the characters.

FIG. 4 shows curves of the potential conditions of the shape elements Land R, resulting e.g. between the three discrete points P P and P atwhich the potential values U U and U exist. Thereupon the followingcriteria may be read.

For shape element L:

( x+1 x x-1 i and ( x x-1+ x+1) For shape element R:

( x-1 x x+1 The shape element G, as likewise results from the potentialcondition according to FIG. 2, is determined by (U' will be describedhereinafter.)

In the case of a closed field margin the same potential within thepotential field exists at all points within the margin, e.g. U =U Bymeans of these six conditions the three shape elements L, R, and G areunambiguously defined and, consequently, capable of being determined.

Following these theoretical considerations the invention will now bedescribed in particular with reference to FIGS. 5-12.

SCANNING OF THE RASTER PATTERN AND SIMULA- TION OF THE NUMERALS WITHINTHE POTENTIAL FIELD Hence, according to the above, at first' the numeralhas to be scanned and the resulting potential values have to beimprinted upon the field. Since the resistor arrangement as shown inFIG. la is used as a field an area quantizing there is required for thescanning of the numerals, that is, the numeral is divided, according toFIG.

5, into a number of partial surface areas b The upper track correspondsto the ordinate value of eleven (11),

the middle track m corresponds to the ordinate values of eight (8); andthe lower track it corresponds to the ordinate value of five all asshown on FIG. 5.

To each of these partial surface areas b y one intersecting point P y ofthe resistor arrangement (FIG. 1a) is assigned, and the arrangement ismade in such a way that a fixed potential U U is imprinted upon thosepoints P y whose associated partial surface area b y exceeds apredetermined blackening content. The other points of the resistorarrangement are not imprinted with any potentials.

In FIG. 5 those partial surface areas b y which deliver a potential U =Uare indicated by hatchlines, while the remaining partial surface areas by are white.

Accordingly, when scanningthe raster pattern only two discrete outputswill be obtained, namely U and 0. These outputs may be obtained by meansof the photocell arrangement as shown in FIG. 6, in which one photocellis provided for each partial surface area b Each photocell arrangementcomprises the photocell F,

the amplifier V and the limiter B. The limiter delivers a digital outputsignal corresponding to the scanning of the raster pattern, i.e. the twovalues U U 0 and U =0.

These two values, in the manner as described hereinbefore, depend uponthe blackening of the scanned partial surface area b It is also possibleto employ a smaller number of photocell arrangements; thus there may beprovided one photocell for respectively each line or column, and the rowof photocells or the pattern itself may be moved trans- 6 latorily.Further it is possible to use one single photocell and to scan thepattern like a television raster. The respective black points are thenretained in storage devices and the corresponding voltages or currentsare then caused to act upon the network.

The above mentioned assignment of the photocell arrangements orrespectively of the partial surface areas b y to the intersecting pointsP y of the resistor arrangement is effected in that respectively oneoutput U y is connected via a diode Di with an intersecting point P,, yin the manner as shown in FIG. 7. At the upper point of the diode Di thepotential U' y exists, while at the lower point that particularpotential which turns up at the corresponding point P y exists.

Accordingly, during the scanning of the raster pattern, the potential Uis imprinted upon all of those points P y whose associated partialsurface areas b y are indicated by hatchlines in FIG. 5. To the otherpoints P y of the resistor arrangement no potentials are imprinted bythe photocell arrangements. Since, the fixed potential zero is appliedto the periphery of the resistor arrangement a potential field iseffected by the scanned numeral, so that upon the scanning, this figurewill be simulated within the resistor arrangement. This is the firststep in recognizing the numerals.

The fact that instead of the direct evaluation of the quantizedpotential conditions the character is at first simulated in thepotential field, and that this potential field is then utilized for thecharacter recognition purpose, bears the advantage that the potentialfield with respect to each individual point, due to the potentialconditions thereof, offers more statements than the arrangementaccording to FIG. 5 giving only the two statements U' :U and U',, =0.

EVALUATION OF THE POTENTIAL FIELD The second step in recognizing thenumerals now consists in the evaluation of the potential field, that is,an examination is carried out as to Whether the shape elements L, R, orG are within the potential field.

FIG. 8 shows the coupling diodes Di of one line of resistors (FIG. 7),which line corresponds for example, to the checking track 0 (FIG. 3). Atthe upper points of the diodes Di there will exist the potentials U' U'U' and at the lower points thereof there will exist the potentials U U yU Electronic circuit elements which, in FIG. 8, are symbolicallyrepresented as rotary switches Dr, are employed for determining thepotential values U,, U U as well as U at three successive points alongone checking track since the checking has to be effected in a cyclicalfashion. The rotary switches are so connected with the resistorarrangement that three successive points in the x-direction may be readout or checked concurrently. Thus the first contact of the rotary switchDrl is connected with the point P while in the rotary switches Dr2 andD14 the first one, and in the rotary switch Dr3 the first two contactsare dead. Since all of the four rotary switches rotate synchronously,the first comparison of voltage can only take place in the thirdposition of the rotary switches. In this position the points P y P y areconnected with the corresponding rotary switches, so that the requiredchecking of the above conditions (l) (4) may be carried out. The rotaryswitch Dr4 is connected with the amplifier point U and it thus servesthe determination of the shape element G.

Appropriately, the rotary switches Dr, which are symbolically shown inFIG. 8, may be electronic gating circuits, which are actuated in a timesuccessive manner. Conventional examples of five such gating circuitsAA, BB, CC, DD and EE are shown in FIG. 9.

The potentials U U and U which are determined at the outputs of therotary switches Drl Dr3 (FIG. 8) are applied to the transistorarrangement as 7 shown in FIG. 10. This arrangement combines thesepotentials for the above conditions (-1) (4) and applies pulses to thelines L or R respectively. The mode of operation of this arrangementwill be understood from the following explanation. The two outputs for Uand U are connected in opposition across the two resistors R1 and R2.The connecting point of the two resistors is applied to the baseelectrode of the transistor T1. The output for the potential U isapplied to the emitter of the transistor T1. In this way an outputsignal is applied to the two-input coincidence gate K1 whenever U /2(U+U (transistors of the p-n-p type are assumed). It will be readilyunderstood by those skilled in the art that n-p-n type junctiontransistors may alternatively be employed, with corresponding changes inthe polarities of the potential applied to the several electrodesthereof along with other changes which are well understood by thoseskilled in the art. The coincidence gates K1, K2 are of known type andrequire the simultaneous application of a voltage upon both inputsthereof in order to render the gate conducting. If, furthermore U U thenthe transistor T2 is capable of conducting, so that a second signal willbe applied to the coincidence gate K1. This signal will then cause theopening of the gate circuit K1 and the application of an identificationsignal for the shape element L to the storage device 5 The output signalof the transistor T1 is concurrently applied to the coincidence gate K2,which will be opened whenever U U and, consequently, the transistor T3conducts. The identification signal appearing at the gate K2 for theshape element R will then be fed to the storage device S As will be seenfrom FIG. 2 of the drawings, the potentials U and U need not be obtainedfor the middle checking track but only the potential U as well as thepotential U',;, for determining the shape element G. In FIG. 11 thecircuit arrangement for obtaining the shape element G with theconditions U U and U U is shown. The potential delivered by a photo cellF upon scanning of a black area is amplified by the amplifier V. Theamplified potential is applied via the limiter B and diode to the pointP y of the resistor arrangement. The rotary switches Dr2 and Dr4 effecta checking of the potentials existing at the two terminals of thediodes. The potential U is applied to the base electrode of thetransistor T4, to whose emitter is applied the potential U Accordinglythe transistor T4 conducts whenever U U i.e. when the correspondingphotocell performs the scanning of a white raster field. Upon conductionof the transistor T4, a signal will be applied to the coincidence gateK3.

The potential U as sampled by the rotary switch Dr2 is applied to theemitter of the transistor T5, to whose base electrode is applied asomewhat lower potential than U In this way the transistor T5 ispermitted to conduct, when U ;U AU and to transmit an output signal tothe K3 which opens and delivers an identification pulse for the shapeelement G to the storage device S Accordingly, an identification signalfor recognizing the shape element G is produced if, and only if, theabove conditions (5) and (6) are met satisfactorily.

In FIG. 12 of the drawings a translator is shown which, in accordancewith the identification signals of the three checking tracks 0, m and uproduces the output signals for the recognized numerals 0 9. Thistranslator substantially consists of coincidence gates, the input leadsof which, in accordance with Table I, are connected with the storagedevices or the outputs thereof. Whenever the storage devices show anabsence of an input signal in all three checking tracks the numeral 1 isindicated. Ka is an and gate which conducts or produces a signal only inthe absence of signals on all 3 inputs. This is symbolically denoted inFIG. 12 by the three input arrows E, E, and 'G' at the coincidence gateKa for the numeral 1.

RECOGNITION OF NUMERAL "2 Following this general description of theinvention there will now be described the recognition of the numeral 2with reference to FIGS. 5 through 12:

On the lines y=2 and 1:3 (FIG. 5), the partial surface areas [1 and onthe line y=4, the partial surface areas b and so on, the hatch-linesindicate when the blackening has exceeded a predetermined thresholdvalue. Consequently, at the outputs of each of the photocells F (FIG.6), which are coupled to these partial surface areas, the scanningpotential U' =U will appear. Accordingly, this potential will beimprinted upon the points P y of the resistor network (FIGS. 1 and 7)assigned to these outputs.

The potential field in the resistor arrangement derived as a result ofthe foregoing will now be checked.

Checking upper track 0.The rotary selectors Dr Dr (FIG. 8) start to runsynchronously. In the first and second position no evaluation iseffected because in the rotary selector Dr the first one, and in therotary selector Dr the first two contacts are dead. In the thirdposition, the selector Dr is connected to the point P the selector Dr tothe point R and the selector Dr to the point P Thus the potentialconditions of these three points may be compared with one another. Aswill be seen from FIG. 5 the rise of potential is approximately linearup to the point P so that no statement can yet result as to whether theshape element L or R exists.

In the next position of the rotary selectors Dr Dr the three points P 11P 11 are checked. Again in this case an unambiguous statement as to theexistence of a shape element L or R is not obtained because of thelinear rise in potential.

However, an unambiguous statement regarding the shape element L resultswhen the three selectors Dr Dr are connected to the points P 11 Pbecause Due to the presence of these potential conditions thecoincidence gate K in FIG. 10 will open, so that as a result a storagepulse will be applied to the storage de- VICfi SL.

Checking lower track u. When performing the checking on track it (FIGS.8 and 10) the same processes as described above in connection with thechecking track 0 will be repeated. Up to the position P 5 P 5 the risein potential is a linear one, so that no statements can yet result as towhether or not the shape element L or R exists.

()n the other hand, when checking the potentials at the points P P theshape element R may be recognized, because now the requirementsAccordingly, in this position of the selectors Dr Dr the coincidencegate K in FIG. 10 opens and delivers a signal to the storage device S Onboth of the checking tracks the conditions for a closed field margincorresponding to the shape element G and do not exist and are neverobtained.

Checking middle track m.-The middle checking track is of no importanceto the recognition of numeral 2, because it only serves fordistinguishing between the numerals and 8, as has already beenmentioned.

As may be seen from Table I, this checking track checks only for thepresence of the shape element G which exists in the numeral 0. From FIG.it will be easily seen that the conditions U =0 and which are requiredfor the shape element G, are not met at any point of the checking trackm.

Since the storage devices 8;, and S for the checking tracks 0 and urespectively, are activated and as shown in FIG. 12, they are connectedto gate K numeral 2 is recognized.

An arrangement may also be made whereby the points P corresponding towhite partial surface areas b y are imprinted with a fixed potential.

In the foregoing the character recognition is described with referenceto the simulation of the characters within a potential field, and theevaluation thereof.

Since, for maintaining the imprinted potential U a predetermined currentI is required, the latter may also be used for character recognition,since characteristic associations exist between the flow ofcurrentwithin the potential field and the shape elements of the characters.

This will now be considered with reference to FIG. 13.

According to the laws of potential theory, the current I flowing into apoint P corresponding to a blackened partial surface area b is greaterthe more exposed this partial surface area projects into nonblackenedpartial surface area. In accordance therewith, characteristic currentstages for the numerals O 9, may be determined which may then be usedfor recognizing the respective numerals. Thus, for example, it issufficient to provide the following five current conditions:

current conditions the blackened partial surface area underconsideration-- 0=near1y no current is strongly screened.

1=small current is lying in an oblong shaped portion of the character.

2=medium current is a screened corner of the character.

3=strong current is an exposed corner of the character.

4=very strong current is a ireely disposed end point of the charac er.

The term screened implies that many black fields exist in theneighbourhood. In FIG. 13 the numerals are provided with the currentcondition identification indicia. The blackening of the numerals willprovide an approximate indication of the current densities. Of course,thedivision into current conditions may also be set up more finely, sothat it will be rendered possible this Table II it will be seen thatnearly all figures differ from each other according to the distributionof the current intensities and, thus, may be recognized. Only the twonumerals 6 and 9 cannot be readily distinguished from one another, butthey will become distinguishable e.g. when examining in what relationthe point with the current condition 3 is to the center of gravity orconcentration of the numeral.

The evaluating arrangement is e.g. capable of measur ing the currents 1,flowing into the points P of classifying these into the diiierent areasof current intensity, and of counting how many times per numeral thedifferent stages appear. The particular distribution thereof will thenbe characteristic for the respective numeral. This distribution is fixedwith respect to distortions (twistings) and displacements of the shape.The fixed distribution with respect to enlargements or reductions insize of the character may be accomplished in that the condition for thecurrent intensity I y is set up relative to the appearing maximum andminimum value. In this way a fixed distribution with respect to changesin the type of numeral will also result.

The measurement of the current intensities I y may be carried out withthe aid of conventional means. A corresponding example for themeasurement is shown in FIG. 14.

In this case the limiter output U' y is connected on one side of aresistor R with the corresponding point P y of the resistor coordinatenetwork. The point A is connected with the emitter of transistor T6,while point B of the resistor is connected to the base electrode of saidtransistor. The collector electrode of the transistor T6 is coupled,across the resistor R4, to a potential which. is negative with respectto potential U' Upon scanning a white partial surface area b y (FIG. 5)the same potential will exist on both sides of the resistor R3, becauseno current is flowing. The transistor T6, therefore, is blocked.However, upon scanning a blackened partial surface area b a certaincurrent will flow into the respective point P of the resistorarrangement, for maintaining the constant potential U Since theintensity of the current depends upon the potential condition of theneighbourhood of the point under consideration different voltage dropsover the resistor R3 are produced. The transistor T6 is thus caused toconduct more or less current. Consequently, also the current flowingacross the resistor R4 has different intensities, corresponding to theabove mentioned current stages 0 4. Because of this difl'erentpotentials will appear at point C.

The point C, therefore, may be connected with a logic circuit in whichthe various conditions are evaluated character recognition. This logiccircuit also serves to determine therepetition rate of the individualconditions per character. The logic circuits, as required to this endare sufliciently known in the art and, therefore, do not need to beparticularly described herein.

The described automatic character recognition methods are ratherinsensitive to type variations. Likewise it is easy to adjust to anydifferences in size when first determining (e.g. with the aid of specialkinds of photocells) the upper or lower margin of the characters and,thereafter, adjusting the photocells to the actual scanning operation.

While the invention has been described in connection with recognition ofnumerals, it will be understood that it is equally eifective torecognize other characters such as letters of the alphabet or any othertype of indicia.

While I have described above the principles of my invention inconnection with specific apparatus, it is to be clearly understood thatthis description is made only by way of example and not as a limitationto the scope of my invention as set forth in the objects thereof and inthe accompanying claims.

What is claimed is: 1. A character recognition system comprising an im-1 1 pedance plane, means for maintaining the periphery of said plane ata fixed electrical potential, means for sensing portions of the outlineof a character to be recognized, means for deriving electricalpotentials differing from said fixed potential from said sensing means,means for applying said potentials to separate coordinate points of saidplane, respectively, whereby said plane will provide a resultantpotential field, means for scanning predetermined coordinate points in aplurality of lines across said plane for detecting the potentialsthereof, and means for comparing said detected potentials for derivingan output corresponding to said character.

2. A character recognition system as claimed in claim 1, wherein saidplane comprises a plurality of resistors arranged in a coordinate arraydefining a plurality of vertical and horizontal rows.

3. A character recognition system as claimed in claim 1, wherein saidsensing means comprises ray-energy responsive elements.

4. A character recognition system as claimed in claim 1, wherein saidmeans for deriving electrical potentials from said sensing meanscomprises amplifier-limiter elements.

5 A character recognition system as claimed in claim 1, wherein saidmeans for applying said potentials to said plane comprise a plurality ofunidirectional current carrying elements interposed intermediate saidcoordinate points and said means for deriving electrical potentials,respectively.

6. A character recognition system as claimed in claim 1, wherein saidcomparison means comprises a plurality of storage devices each adaptedto store information regarding particular parameters of scannedcharacters, a separate coincidence gate element for controlling theoperation of each of said storage devices, switch means intermediatesaid scanning means and said gate elements for controlling operationthereof, there being at least two of said switch means coupled to eachof said gate elements to effect operation thereof.

7. A character recognition system comprising means for electricallysimulating a character shape as a predetermined potential in a potentialfield, means for determining spatial potential gradients in said field,and means for evaluating said gradients whereby the character isunambigously determined.

8. A character recognition system as claimed in claim 7 in which themeans for determining said gradients includes the constitution ofspatial derivatives.

9. A character recognition system comprising an impedance matrix meansfor electrically simulating a character shape as a first potential insaid matrix, means for maintaining the periphery of said matrix at apredetermined second potential, means for determining spatial potentialgradients in said matrix, and means for evaluating said gradientswhereby the character is unambiguously indicated.

10. A character recognition system comprising a resistor network havinga first fixed potential at its periphery, means for electricallysimulating a character as a fixed second potential in said network,means for determining potential gradients in said network, and means forevaluating said gradients whereby the character is unambiguouslyindicated.

11. A character recognition system as claimed in claim 10 in which themeans for evaluating said gradients includes the approximateconstitution of spatial derivatives.

12. A character recognition system comprising a coordinate network ofresistors, means for maintaining the periphery of said network at apredetermined potential, means for impressing potentials difiering fromsaid predetermined potential on intersecting points of the resistornetwork corresponding to respective partial areas of the character,means for determining the changes in potential between coordinate pointsin said network, means for evaluating said changes in potential, meansfor translating the evaluation into indicia corresponding to thecharacter.

13. A character recognition system comprising a coordinate network ofresistors maintained at a first potential, transducer means adapted toscrutinize discrete areas of a character and give potentials relative toindicia on said areas, means for assigning said potentials from saiddiscrete areas on a one to one basis to corresponding intersectingpoints in said network to induce a potential field in said network,means for scanning said network and said transducer potentials in aplurality of tracks and deriving potentials therefrom, means forcomparing said last mentioned potentials within each track anddetermining a shape element therefrom, means for translating the shapeelements derived at said tracks into an indication of the character.

14. A character recognition system comprising a coordinate network ofresistors maintained at a first potential, a plurality of transducerscoupled to intersecting points in said network on a one to one basisadapted to scrutinize discrete areas of a character and give secondpotentials relative to indicia thereon, unidirectional current carryingmeans connected between each transducer and its associated intersectingpoint, selector means for scan- .ning transducer potentials and networkpoints in a plurality of tracks and deriving potentials therefrom, meansfor comparing the derived potentials within each track and determining ashape element, means for storing said shape element, means fortranslating the stored shape element of all of the tracks into anindication of the character.

15. A character recognition system as claimed in claim 14 in which theselector means comprises a plurality of cyclically rotating switchesadapted to scan successive intersecting points on a track and successivetransducer potentials associated with those points.

16. A character recognition system as claimed in claim 14 in which thetransducer includes an amplifier-limiter.

17. A character recognition system comprising a coordinate network ofresistors grounded at its periphery, a circuit coupled to eachintersecting point in said network, said circuit comprising a diode, alimiter, an amplifier, and a photocell respectively serially connected,the photocells being adapted for reading discrete areas of characterswhereby each discrete area corresponds to an intersecting point in saidnetwork, a plurality of tracks in said resistor network, cyclicallyrotating reading means for each track adapted to read successiveintersecting points and successive limiters, a shape determinercomprising transistors, and gates, and storage devices coupled to eachof said reading means for determining and storing a shape element, atranslator comprising a plurality of and gates and coupled to all of theshape determiners for indicating the recognized character.

18. A character recognition system comprising means for electricallysimulating a character shape as predetermined potential in a potentialfield, means for measuring the current necessary to simulate saidcharacter and means for evaluating said currents whereby the characteris unambiguously determined.

19. A character recognition system comprising means for electricallysimulating a character shape as a predetermined potential in a potentialfield, means for measuring the currents in said field, and means forevaluating said currents whereby the character is unambiguouslydetermined.

20. A character recognition system comprising means for electricallysimulating a character as a first potential in an impedance matrix,means for keeping the periphery of said matrix at a predetermined secondpotential, means for measuring the currents necessary to simulate saidcharacter and means for evaluating said currents whereby the characteris unambiguously determined.

21. A character recognition system comprising a coordinate network ofresistors, means for maintaining the periphery of said network at apredetermined potential,

means for impressing potentials differing from said first potential onintersecting points of the resistor network corresponding to respectivepartial areas of the character, means for measuring the currentnecessary for maintaining the impressed potentials on intersectingpoints of the resistor network, means for evaluating said currents, andmeans for translating the evaluation into indicia corresponding to thecharacter.

References Cited in the file of this patent UNITED STATES PATENTSZworykin Nov. 4, 1952 Reed Sept. 22, 19-59 Peek Oct. 6, 1959 Merritt eta1. Feb. 9, 1960 Taylor I an. 9, 1962

7. A CHARACTER RECOGNITION SYSTEM COMPRISING MEANS FOR ELECTRICALLYSIMULATING A CHARACTER SHAPE AS A PREDETERMINED POTENTIAL IN A POTENTIALFIELD, MEANS FOR DETERMINING SPATIAL POTENTIAL GRADIENTS IN SAID FIELD,AND MEANS FOR EVALUATING SAID GRADIENTS WHEREBY THE CHARACTER ISAMBIGUOUSLY DETERMINED.